For example, Patent Document 1 discloses an illumination apparatus which is of a chip-on-a-board (COB) type. This kind of illumination apparatus includes a resin substrate having a white surface, a plurality of light emitting diode strings, a reflector, and a sealing member.
The light emitting diode strings linearly extend along the surface of the resin substrate and are arranged parallel to each other at intervals in a direction orthogonal to a direction along which each light emitting diode string extends. The reflector is bonded to the surface of the resin substrate to surround the light emitting diode strings. The sealing member is made of a transparent silicone resin having a fluorescent material mixed therein. A region surrounded by the reflector to seal the light emitting diode strings is filled with the sealing member.
Each of the light emitting diode strings includes a plurality of light emitting diode elements. The light emitting diode elements are aligned at intervals. Each light emitting diode element has a pair of element electrodes and is bonded to the surface of the resin substrate by using a die bond material.
The light emitting diode elements adjacent to each other in the direction along which the light emitting diode string extends are electrically connected through a bonding wire. One end of the bonding wire is connected to the element electrode of one light emitting diode element in the light emitting diode elements adjacent to each other. The other end of the bonding wire is connected to the element electrode of the other light emitting diode element. Therefore, the light emitting diode string has a configuration that the light emitting diode elements are connected in series.
According to a conventional illumination apparatus, the element electrodes of each light emitting diode element are aligned in the direction along which the light emitting diode string extends. Therefore, when the light emitting diode string is seen in a plan view, the bonding wires are wired in a straight line in the direction along which the light emitting diode string extends.
Furthermore, all the light emitting diode strings have the same entire length. When the light emitting diode strings are arranged parallel to each other at intervals, many light emitting diode elements are regularly arranged in a matrix form in the substantially entire region surrounded by the reflector.
According to the thus configured illumination apparatus, relay bonding pads to which the bonding wires are bonded are not required between the light emitting diode elements adjacent to each other in the direction along which the light emitting diode string extends. Therefore, a pitch between the light emitting diode elements adjacent to each other can be reduced, which is suitable for high dense arrangement of many light emitting diode elements. Moreover, if the pitch between the light emitting diode elements adjacent to each other is narrowed, a length of the bonding wire cutting across the light emitting diode elements adjacent to each other can be reduced when the light emitting diode string is seen in a plan view. As a result, deformation of the bonding wire caused because of a weight of the sealing member can be suppressed.